Hand and foot contamination monitors are known conventional surface contamination monitors that are installed in facilities where radioactive substances are handled, such as nuclear power plants and hospitals, for inspection of surface contamination by radioactive substances that are adhered to the hands, feet and clothing of personnel in such facilities. A hand and foot contamination monitor measures radiation (α rays, β rays and γ rays) emitted by a radioactive substance, sounds an alarm when a measurement value exceed an alarm level, and causes the contaminated areas to be displayed on a liquid crystal display.
As radiation detection sensors in such hand and foot contamination monitors there are used, for instance, GM counters, gas flow counters and scintillator-type radiation detectors. GM counters and gas flow counters detect radiation on the basis of the gas-ionizing action of radiation. In scintillator-type radiation detectors, light emitted by a scintillator on account of radiation is condensed by waveguides, and the condensed light is amplified by a photomultiplier tube, such that radiation is detected on the basis of amplified signals (for instance, Japanese Patent Application Publication No. 2003-167059).
Semiconductor-type radiation detectors are also known as ordinary radiation detection sensors. In semiconductor-type radiation detectors, radiation strikes a radiation detection element made up of a semiconductor, such as silicon (Si), and charge generated by ionization on account of the radiation is outputted in the form of electric signals, whereby radiation is detected.
Patent document 1: Japanese Patent Application Publication No. 2003-167059
Patent document 2: Japanese Patent Application Publication No. S63-193088
Hand and foot contamination monitors and surface contamination monitors are used not only for inspection of contamination from radioactive substances on the surface of personnel and objects that enter and leave a facility where radiation is worked with, but also, as the case may require, for primary inspection of surface contamination by radioactive substances at locations, within the facility, where radioactive substances are handled. However, using radiation detection sensors in the form of GM counters, gas flow counters, and scintillator-type radiation detectors was problematic in that the hand and foot contamination monitor or the surface contamination monitor was large and heavy, on account of the large size of the radiation detection sensor devices, which precluded the monitor from being relocated to the inspection site in a simple manner.
Thus, smaller and lighter hand and foot contamination monitors can be potentially realized by using semiconductor-type radiation detectors, having a comparatively small device scale, as radiation detection sensors in hand and foot contamination monitors. Also, a semiconductor-type radiation detector that allows maintaining the radiation detection performance over long periods of time would be desirable as a radiation detection sensor in a hand and foot contamination monitor.